9. Renal Embryology Flashcards by Priyanka Barad

What does the intermediate mesoderm produce?

Urinary (1st) and genital system

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What is the urogenital ridge?

Longitudinal bands of mesoderm that form on each side of the dorsal aorta

-forms nephrogenic cord (which forms pronephros, mesonephros, & metaphros)

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What is the order the nephrite structures form?

Urogenital ridge —> nephrogenic cord —> pronephros —> mesonephros —> metanephros

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What is the pronephros?

Bilateral, transitory structures that appear early in 4th week in cervical region

Degenerates by 24-25 days (except for the ducts)

IMP: bc they initiate cascade leading to formation of definitive kidney (w/o it nothing gets the ball rolling)

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Where are the pronephric ducts located

Run caudally & open into the cloaca

Persist & used by mesonephros

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What is the mesonephros?

Bilateral transient structure that appears later 4th week caudal to pronephros

-includes mesonephric ducts (made 1st) & mesonephric tubules (induced by ducts from surrounding intermediate mesoderm)

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What do the mesonophric tubules form?

Renal corpuscles

medial end = glomerular capsule (cup-shaped)

& glomerulus (not of caps)

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What do the mesonephros do?

Fxn as interim kidneys from 6-10 weeks

produce small amount of urine

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What happens to mesonephros after 10 weeks

Females - regress

Male- form efferent ductules

-degenerate by week 12

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What is the metanephros

-arise during 5th week at causal end of mesonephric duct —> induce ureteric bud

=ureteric bud & metanephric blastema

-form fxnal & definitive kidney by 9-10th week

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Where do the parts of the metanephros form

Ureteric bud - outgrowth of mesonephric ducts

Metanephric blastema = from sacral region of nephrogenic cord

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What is the purpose of urine production in utero

makes amniotic fluid
w/o = oligohydraminos —> potters sequence

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Where is waste filtered in embryo

Placenta

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How do the collecting tubules form

Ureteric bud elongate to sacral portion of intermediate mesoderm & penetrate the blastema —> form renal pelvis

-cranial part of buds —> collecting tubules - 1st generation = major calices & then 2nd = mini calices

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How does the nephron develop

Metanephrogenic blastema form metanephric vesicles

—> vesicles elongate to form metanephric tubules

—> proximal ends form glomerular capsule & get invaded by glomeruli

& other end of tubule differentiate into PCT, DCT and nephron loop –> then DCT contact arched collecting tubule

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How does the kidney ascend

permanent kidney lies w/I pelvis and gradually ascend into abd —> in adult position by 9th week & in contact with suprarenal glands

How do the kidneys receive blood supply

First branch from common iliac & the definitive renal As from abdominal aorta

-early renal As & common iliac then involute and disappear

Why does the hilum rotate medially 90 degrees

-allow correct orientation of vasculature

What structures does the ureteric bud form

Ureter

Renal pelvis

Major & minor calyces

Collecting ducts

What structures does the metanephric blastema form

Bowman’s capsule

PCT

Loop of hence

DCT

what is the cause of unilateral renal agenesis & bilateral renal agenesis

ureteric bud doesn’t branch off mesenephros duct & doesnt induce metanephric blastema to from from sacral end

what happens in duplication

abnormal divison of uretirc bud

incomplete = divide kindey & bifid ureter

complete = double kidney & bifid ureter/separate ureters

what is horseshoe kidney

fusion of inferior poles

ascent prevented by inf mesenteric A & have low lying kidney

asym

what are accessory renal vessels

multiple renal As

can obstruct the ureter by compressing it –> leading to hyrdonephrosis dilate pelvis & ureter –> filtrate backed up into kidney

get flank pain

also = end As so if damaged or ligated - can cause ischemia

what is polycystic kidney disease

auto recessive mutation of PKHD1 cysts present in both kindeys renal insufficiency -25% associated with pul hypoplasia

what is multicystic dysplastic kidney disease

abdnormal development of renal system cysts are likely dilations of loop of henle usually only one kidney is affected

what is the urogenital sinus

from ventral cloaca (distal hindgut) cirtical for bladder & urethral development

what are the parts of the urogential sinus

1. **vesical part: **forms most of urinary bladder 2. **pelvic part:** forms neck of bladder & urethera (female) & prostatic urethera (male) 3. **phallic part:** forms lining of vaginal vestibule (female) & spongy urethera (male)

what is the urorectal septum

seperates the urogenital sinus & anorectal canal expands & contributes to wall of perinium seperate the urinary and digestive tracts

what are the steps of forming the trigone

week 4-6 mesonephric duct incorporate into post wall of bladder --\> ureteric bud is attached and connects the bud opening into the bladder wall --\> openings of mesonephric duct are carried inferiorly to the pelvic urethra ==\> form trigone (region where mesonephric & ureteric ducts blend with post wall of bladder)

what are the parts of the bladder and what are they derived from

epithelium - endoderm (urogenital sinus) submucosa & muscularis = splanchnic mesoderm trigone = intermediate mesoderm (mesonephric ducts)

what is the allantois

continous with bladder - extends from apex of bladder to umbilicus = fetal mem developed from hind gut --\> constricts and forms urachus will form the median umbilical ligament

what is exstrophy of the bladder

arise during body folding in 4th week --\> defective closure of the ventral abd wall expose mucosa of the post wall of bladder

what is epispadias

urethral opening is the dorsum of the genital tubercle rather than on ventral side occurs with extrophy

what is the difference btn urachal cysts, sinus & fistulas

urachal cyst: remnant of epithelial lining of urachus bc cord doesnt fill in completely - enlarge & infected urachal sinus: end of urachus remain open into the inf bladder or umbilius (sup part) urachal fistula: entire urachus remains patent --\> allow urin gto escape from umbilical orifice

what are the parts of the suprarenal gland & what do they produce

* **Cortex** * zona glomerulosa: mineralocorticoids * zona fasciculata: glucocorticoids * zona reticularis: sex hormones * **Medulla** * chromaffin cells that secrete NE & Epi

what does the medulla of the suprarenal gland develop from

NCCs they migrate thru intemediate mesoderm to form adrenal medula & differntiate into chromaffin cells

how does the cortex of the suprarenal gland form

week 5 coelomic epithelium (**somatic mesoderm**) delaminate & enter surrouding mesoderm --\> then regress in 2nd month PN to make zona glomerulosa, fasciculata & reticularis fetal cortex will secrete DHEA --\> converted to estradiol (\*essential for pregnancy\*)